This invention relates to a device for detecting defects of the so-called non-woven fabric manufactured in the form of cloth without weaving.
In the prior art, for the grading of the quality of a non-woven fabric, the non-woven fabric once wound in the form of a roll is unwound and passed over an inspection table of frosted glass and, in this case, light of a fluorescent lamp is applied to the underside of the frosted glass to facilitate finding of defects of the non-woven fabric and an inspector judges the defects by visual inspection and counts the defects of respective kinds with counters by manual operation. That is, the defect of the non-woven fabric is classified into a hole having a diameter more than 2 mm, a fold bar which is folding or overlapping of a certain area of the non-woven fabric, a heavy filling bar that a certain area of the non-woven fabric is remarkedly thick as compared with the neighboring area and a weight bar that the non-woven fabric is a little thick or thin over a wide area. These four defects are found out by visual inspection of the non-woven fabric passing over the aforementioned frosted glass and counted by counters respectively corresponding to the four kinds of defects. The detection of the defects of the non-woven fabric in the prior art is achieved by such visual inspection and subject to individual inspectors' judgement and not so objective. Further, since the non-woven fabric is travelling the inspection requires a considerable amount of skill and is subject to each inspectors' individual difference in judgement as to the defects. That is, decision of the defects is likely to vary greatly according to the particular inspector, so that the inspection is subjective and inaccurate. Moreover, such visual inspection is very laborious. In addition, it is impossible to detect the defects by such a conventional method in the course of the fabrication of the non-woven fabric, so that it is necessary for visual inspection to spread the non-woven fabric once rolled after manufactured. Thus, with such conventional method of inspection, it is impossible to effect grading of the quality of non-woven fabrics during their manufacture for classifying them according to the quality or for obtaining non-woven fabrics of the same quality by controlling the manufacturing process.
The object of this invention is to provide a non-woven fabric defect detecting device which is capable of automatic, subjective and accurate detection of various defects of a non-woven fabric in the course of its manufacture and enables grading of the quality of the fabric, if necessary.